In the field of recreational vehicles (e.g., motorcycles, all terrain vehicles (ATVs), snowmobiles, sport trucks, dune buggies, sandrails, and the like) protective helmets are often worn to protect the user's head. Particulates such as sand and dust may enter the helmet during use and interfere with the user's ability to operate the vehicle. The more particulates a helmet keeps away from the user's face and eyes, the more comfortable the user will be. Even a few particulates in a user's eye may cause great discomfort.
Protective helmets are typically subjected to standardized performance tests to ensure the user is as safe as possible if a collision occurs. The Department of Transportation (DOT) and Snell are two major organizations that set safety standards for crash-helmets in the United States. DOT sets minimum standards for all helmets designed for motorcyclists and other motor vehicle users. The standard is Federal Motor Vehicle Safety Standard 218 and is codified at 49 C.F.R. § 571.218. The Snell 2000 Standard for Protective Headgear establishes performance characteristics for helmets for use in open motorized vehicles such as motorcycles, ATVs, and snowmobiles.
The DOT subjects crash-helmets to an impact attenuation test. Impact attenuation is determined by measuring the acceleration experienced by a helmeted test headform during a collision. The helmeted headform is dropped on both a hemispherical and flat steel anvil. The height for the helmet and test headform combination fall onto the hemispherical anvil is set so that the impact speed is 5.2 m/sec. The minimum drop height is 138.4 cm. The guided freefall drop height for the helmet and test headform combination unto the flat anvil is set so that the minimum impact speed is 6.0 m/sec, with a minimum drop height of 182.9 cm.
When an impact attenuation test is conducted as described above, the following criteria are used to determine if a helmet passes; the test headform must not experience a peak acceleration over 400 G, accelerations in excess of 200 G must not exceed a cumulative duration of 2.0 milliseconds, and accelerations over 150 G must not exceed a cumulative duration of 4.0 milliseconds. The Snell impact management test involves a series of controlled impacts. First, the helmet is positioned on a head test platform. The helmeted headform is then dropped in guided falls onto test anvils. The impact energy must be a minimum of 150 Joules. If the peak acceleration imparted to the headform exceeds 300 G, the helmet fails.